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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 6 |
| 4 | 18 |
| 5 | 27 |
| 6 | 82 |
| 7 | 138 |
| 8 | 390 |
| 9 | 644 |
| 10 | 1837 |
| 11 | 3242 |
| 12 | 8835 |
| 13 | 15271 |
| 14 | 42086 |
| 15 | 76403 |
| 16 | 203377 |
| 17 | 361636 |
| 18 | 974089 |
| 19 | 1802727 |
| 20 | 4718991 |
| 21 | 8559441 |
| 22 | 22673687 |
| 23 | 42562209 |
| 24 | 110006420 |
| 25 | 202537249 |
| 26 | 529643894 |
| 27 | 1005279834 |
| 28 | 2572145945 |
| 29 | 4791823354 |
[1,1,4,6,18,27,82,138,390,644,1837,3242,8835, 15271,42086,76403,203377,361636,974089,1802727, 4718991,8559441,22673687,42562209,110006420, 202537249,529643894,1005279834,2572145945, 4791823354] |